Tool and method for controlling depth of polluted layer on surface of titanium alloy

Abstract

The invention discloses a tool and method for controlling the depth of a contaminated layer on the surface of titanium alloy, and the tool comprises a box body which is provided with an opening in the top and is used for accommodating a titanium alloy part to be treated; the top cover assembly is connected with the opening of the box body, the top cover assembly comprises a ceramic matrix composite one-way cover and a one-way exhaust valve, a plurality of vent holes are formed in the ceramic matrix composite one-way cover, and the one-way exhaust valve is installed at the vent holes; the sealing piece is arranged at the joint of the box body and the sealing cover assembly, and the sealing piece is an annular aerogel gasket; the internal bearing mechanism comprises a plurality of internal bearing assemblies, and the plurality of internal bearing assemblies are arranged in the box body; and the pre-vacuumizing valve is arranged on the box body. According to the method, the depth of the surface pollution layer of the titanium alloy subjected to heat treatment can be stably controlled within 0.05 mm and is obviously superior to the upper limit of 0.08 mm required by the existing industrial standard.

Description

Technical Field

[0001] This invention belongs to the technical field of titanium alloy surface contamination layer technology, and in particular relates to a tooling and method for controlling the depth of contamination layer on titanium alloy surfaces. Background Technology

[0002] Titanium alloys have advantages such as being lightweight, high-strength, non-magnetic, and corrosion-resistant. They are widely used in aviation, aerospace, shipbuilding, and rail transportation to manufacture various types of load-bearing components and fasteners, greatly improving the service performance of equipment and providing strong support for the development and upgrading of next-generation equipment. They play an important role in national economy and national defense security.

[0003] Currently, with the continuous development of science and technology and the urgent need to improve equipment performance, the use of titanium alloy materials in various equipment is gradually increasing. For example, the United States, as a military power, highly values ​​the strategic worth of titanium alloys. In its SR-71 "Blackbird" strategic reconnaissance aircraft, titanium alloys account for 93% of its airframe weight; in the F-22, titanium alloys account for 41% of its total weight; and in the TF31 aero-engine, titanium alloys account for 33%. In recent years, my country has also made significant progress in the field of titanium alloy technology. For instance, the C919 large passenger aircraft uses 9% titanium alloys, exceeding the Boeing 777's 7%; advanced fighter jets use over 20% titanium alloys; and the Liaoning aircraft carrier also extensively uses titanium alloys. The amount of titanium alloys used has become an important international indicator of equipment advancement, and the use of titanium alloy materials and components has increased significantly.

[0004] While titanium alloys offer numerous performance advantages over traditional alloy steels, their chemical reactivity makes them highly susceptible to oxidation at high temperatures, readily forming a dense and brittle oxide layer. Standards define this dense α-layer as a contamination layer, which significantly reduces the plasticity and toughness of titanium alloys, leading to component failure. In engineering applications, due to their heat-treatable nature, titanium alloy components are typically manufactured using a solution treatment followed by aging process to achieve the desired strength and plasticity to meet service requirements. To control contamination during heat treatment, the American standard AMS 2801, "Heat Treatment of Titanium Alloy Parts," specifies that heating above 704°C should be performed under vacuum, with the vacuum level controlled below 1.33 Pa. Domestic regulations also address contamination control, but these measures often fail to prevent contamination layer formation; even after vacuum heat treatment, components still exhibit a deep contamination layer on their surface. Taking aerospace fasteners as an example, the higher the heating temperature, the deeper the contamination layer, exceeding 0.2mm in maximum depth. However, several authoritative standards, such as HB8025 "TC16 General Specification for Titanium Alloy MJ Threaded Bolts and Screws," clearly stipulate that the surface contamination layer depth must not exceed 0.08mm. Clearly, the heat treatment control methods recommended in standard documents such as AMS2801 cannot meet product standard requirements. The titanium alloy contamination layer problem has become a major challenge in the manufacturing process of aerospace titanium alloy fasteners. Currently, there is no effective control method in the industry, and processing can only be carried out through surface removal methods. Typical removal methods include turning, grinding, and pickling, which bring many adverse effects to the production process. 1. After heat treatment, several additional processing steps such as pickling or pickling are required, which increases manufacturing costs and significantly extends the product processing and production cycle, resulting in a waste of production resources. 2. The method of removing the contamination layer requires that the amount to be removed be reserved when the product is put into production. The additional raw material size needs to cover the maximum depth of the contamination layer, resulting in waste of raw materials. 3. Surface removal will disrupt the original flow lines of the raw materials, leading to an increase in original defects in the parts, a decrease in strength, fatigue and other properties, and an inability to fully utilize the material's performance.

[0005] 4. Removing the contamination layer will introduce additional defects to the surface of the parts. For example, removing the contamination layer by turning will introduce fine tool marks, which will become crack sources and reduce service life; removing the contamination layer by pickling poses a risk of hydrogen absorption, which can lead to brittle fracture of the product.

[0006] This invention addresses the problem of surface contamination layers on titanium alloy parts. By controlling the influencing factors of contamination layer formation and designing suitable heat treatment tooling, it solves the problem of surface contamination layers during the heat treatment process of titanium alloy parts, improves the control capability of the product manufacturing process, and promotes the technological development of the titanium alloy parts industry. Summary of the Invention

[0007] In view of this, the present invention aims to provide a tooling and method for controlling the depth of the contamination layer on the surface of titanium alloys, so as to solve at least one technical problem in the background art.

[0008] To achieve the above objectives, the technical solution of the present invention is implemented as follows: A tooling for controlling the depth of contamination layer on titanium alloy surfaces, comprising: The enclosure has an opening at the top for accommodating titanium alloy parts to be processed. The top cover assembly is connected to the opening of the box body. The top cover assembly includes a ceramic matrix composite one-way cover and a one-way exhaust valve. The ceramic matrix composite one-way cover is provided with several vent holes, and the one-way exhaust valve is installed at the vent holes. A sealing element is provided at the junction of the housing and the sealing cover assembly, and the sealing element is an annular aerogel gasket; The internal support mechanism includes several internal support components, which are housed within the enclosure. A pre-vacuum valve is located on the housing.

[0009] Furthermore, the internal load-bearing components include tooling mesh and pad blocks; One end of the tooling mesh is set inside the box via a rotatable bearing, and the other end is set on the top of the pad block; The pad is placed inside the housing and corresponds to the position of the rotatable bearing.

[0010] Furthermore, the tooling mesh is woven from high-temperature resistant metal wire; And / or, the pad is made of stainless steel or a nickel-based high-temperature alloy; And / or, the number of internal carrier components is at least 2.

[0011] Furthermore, the one-way exhaust valve is a reed-type or diaphragm-type vacuum differential pressure valve, which opens to exhaust when the internal air pressure is higher than the external pressure, and closes when the internal air pressure is equal to or lower than the external pressure.

[0012] Furthermore, the annular aerogel gasket is a zirconia annular aerogel gasket.

[0013] A method for controlling the depth of a contamination layer on a titanium alloy surface, using the aforementioned tooling for controlling the depth of a contamination layer on a titanium alloy surface, is characterized by comprising the following steps: S1: Pretreatment of titanium alloy parts to be processed; S2: Lay titanium shavings layer by layer on the internal load-bearing components, place the titanium alloy parts to be processed on the titanium shavings, and then lay them on with titanium shavings. S3: Perform solution treatment and aging treatment.

[0014] Furthermore, the pretreatment of the titanium alloy parts to be treated in step S1 includes the following steps: A1: A multi-tank cleaning system is used to clean the titanium alloy workpiece to be treated. The cleaning system includes a first tank, a second tank, a third tank, a fourth tank, a fifth tank, and a sixth tank arranged in sequence; the first and second tanks are alkaline metal cleaning agent tanks; the third tank is a clean water spray tank; the fourth tank is an acidic cleaning agent tank; the fifth tank is a hot water rinsing tank; and the sixth tank is a spin-drying tank. A2: Perform wet sandblasting and drying on the cleaned workpiece.

[0015] Furthermore, the concentration of the alkaline metal cleaning agent in both the first and second tanks is 2% to 5%, the heating temperature is 60 to 80°C, and the processing time of the workpiece in each tank is 20 to 40 minutes. And / or, the third tank is cleaned by a water spray tank at room temperature or low temperature for 5 to 10 minutes. And / or, the acid cleaning agent concentration in the acid cleaning agent tank of the fourth tank is 1% to 3%, the heating temperature is 60 to 80°C, and the treatment time is 5 to 10 minutes; And / or, the hot water rinsing time in the fifth tank is 5 to 10 minutes; And / or, the heating temperature of the spin-drying tank in the sixth tank is 60-80℃, and the spin-drying time is 20-40 minutes; And / or, the cleaned workpiece surface should reveal the original metal color, with no visible black spots, black patches or water stains remaining, and the operator must wear clean gloves during handling; And / or, in step A2, the sandblasting pressure for wet sandblasting the cleaned workpiece is 0.5 to 0.8 MPa, and the sandblasting time is 20 to 40 minutes; And / or, the drying temperature in step A2 is 80~110℃, and the holding time is 1~3h.

[0016] Furthermore, in step S2, the titanium chips are obtained by turning, are spiral in shape, and have a length of not less than 2 cm. The total volume of the titanium chips is 3 to 5 times the total volume of the part. After laying the titanium chips, titanium wire is used to fix the titanium chips to the part. Further, in step S3, the solution heat treatment involves holding at 600–700℃ and 800–900℃ for 25–35 min; followed by holding at 1000–1050℃ for 55–65 min; the process vacuum degree is 1.3–1.4 × 10⁻⁶.-2 Pa; After the heat preservation is completed, cool to room temperature in argon gas; In step S3, the aging heat treatment does not require reloading of the parts. The chamber is directly transported to the aging furnace, the temperature is 700-800℃, the time is 3-5 hours, and the process vacuum degree is 1.33×10⁻⁶. -2 Pa; The heating rate for solution treatment and aging in step S3 shall not exceed 25°C / min; The protective or cooling atmosphere used in the solution heat treatment and aging heat treatment in step S3 is argon, and its dew point is not higher than -55℃.

[0017] Compared with existing technologies, the tooling and method for controlling the depth of contamination layer on titanium alloy surfaces described in this invention have the following advantages: 1. The tooling and method for controlling the depth of the contamination layer on the surface of titanium alloys proposed in this invention represent a breakthrough in technology. Through integrated tooling design and systematic process control, this method can stably control the depth of the surface contamination layer of titanium alloys after heat treatment to within 0.05 mm, significantly better than the existing industry standard limit of 0.08 mm. Its core lies in the protective mechanism combining a ceramic matrix composite unidirectional cap with a titanium chip protective layer. This effectively isolates external contaminants and adsorbs residual gases during high-temperature heat treatment, thereby inhibiting the formation of the contamination layer at its source. This technological achievement not only solves the long-standing problem of contamination control in the processing of titanium alloy parts in high-tech fields such as aerospace, but also improves the surface integrity of the parts, avoiding secondary defects such as microcracks and hydrogen embrittlement caused by subsequent removal of the contamination layer, and significantly enhancing the fatigue life and service reliability of the parts.

[0018] 2. This solution offers significant cost savings and efficiency improvements. By avoiding the contamination layer removal processes required in traditional methods, such as turning, grinding, or pickling, it directly reduces processing steps and time, shortening the overall production cycle by approximately 20% to 30%. Simultaneously, since there is no need to reserve allowances for subsequent processing, raw material utilization is improved, effectively reducing material waste and procurement costs. The tooling itself is durable and reusable, and the titanium shavings protection material is recyclable, further enhancing the solution's economic viability and sustainability. For companies mass-producing titanium alloy fasteners, structural components, and other products, this translates to substantial cost reductions and increased production capacity.

[0019] 3. This solution demonstrates a high degree of systematicity and operability. From the six-tank cleaning, wet sandblasting, and precision drying in the pretreatment process, to the furnace loading specifications, stepped heating, vacuum degree, and atmosphere control in the heat treatment process, each step has clearly defined parameter ranges and operational requirements, forming a complete process control chain. The design of specialized tooling makes furnace loading, transfer, and process monitoring simpler and more reliable, and easily integrated into existing production lines. This standardized and modular control mode not only ensures batch stability of product quality but also reduces over-reliance on operator experience, which is conducive to the standardized promotion and large-scale application of the technology.

[0020] 4. This solution also offers significant social benefits in terms of environmental protection and safe production. By completely abandoning the traditional pickling and decontamination process, the risks of acidic wastewater discharge and heavy metal pollution are fundamentally eliminated. Simultaneously, the potential for hydrogen embrittlement fracture in titanium alloy parts due to hydrogen absorption during pickling is eliminated, thus enhancing the inherent safety of the product. The adoption of wet sandblasting reduces dust pollution and improves the working environment. The overall process is clean and controllable, aligning with the current trend of green and refined development in manufacturing, and providing the titanium alloy processing industry with a high-performance, low-cost, and environmentally friendly sustainable development path. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of a tooling for controlling the depth of contamination layer on the surface of titanium alloys proposed in this invention; Figure 2 This is a schematic diagram of a ceramic matrix composite one-way cover for a tooling device for controlling the depth of contamination layer on the surface of titanium alloy proposed in this invention. Figure 3 This is a schematic diagram of a one-way exhaust valve for controlling the depth of contamination layer on the surface of titanium alloy, as proposed in this invention. Figure 4 This is a side view of a ceramic matrix composite one-way cover for a tooling device for controlling the depth of contamination layer on the surface of titanium alloy proposed in this invention. Figure 5 This is a schematic diagram of titanium chip laying for a tooling device for controlling the depth of contamination layer on titanium alloy surfaces, as proposed in this invention. Figure 6 This is a schematic diagram of the tooling for controlling the depth of contamination layer on the surface of titanium alloys, as proposed in this invention, showing the layer-by-layer laying of titanium chips and placement of parts. Figure 7 This is a schematic diagram of a ceramic matrix composite unidirectional cover for a tooling device for controlling the depth of contamination layer on the surface of titanium alloy proposed in this invention. Figure 8This is a drawing of the heat-treated titanium alloy part in Embodiment 1 of the present invention; Figure 9 The images show the metallographic structure of the titanium alloy parts after heat treatment in Embodiment 1 of the present invention (a and b are metallographic structures of titanium alloy parts at different magnifications). Figure 10 This is a drawing of the heat-treated part in Comparative Example 1 of the present invention; Figure 11 The metallographic images of the heat-treated titanium alloy parts in Comparative Example 1 of the present invention are shown (a and b are metallographic images of titanium alloy parts at different magnifications). Figure 12 The metallographic images of the heat-treated titanium alloy parts in Comparative Example 2 of the present invention are shown (a and b are metallographic images of titanium alloy parts at different magnifications). Figure 13 The metallographic images of the heat-treated titanium alloy parts in Comparative Example 2 of the present invention are shown (a and b are metallographic images of titanium alloy parts at different magnifications).

[0022] Explanation of reference numerals in the attached figures: 1. Housing; 2. One-way cover made of ceramic matrix composite material; 3. One-way exhaust valve; 4. Annular aerogel gasket; 5. Pre-vacuum valve; 6. Tooling mesh; 7. Pad block; 8. Rotatable bearing. Detailed Implementation

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0024] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0025] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0026] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0027] The pretreatment technology mainly consists of four aspects: control of cleaning quality, control of surface roughness, control of drying degree, and control of furnace cleanliness. The key points of process control are as follows: 1. Cleaning Quality Control: The product to be processed undergoes repeated cleaning in six tanks. Tanks one and two use alkaline metal cleaners with a concentration of 2%–5%; tank three uses clean water spray; tank four uses an acidic cleaner with a concentration of 1%–3%; tank five is a hot water tank; and tank six is ​​a spin-drying tank. Tanks one, two, four, and six are heated to 60–80℃. The operating time for tanks one, two, and six is ​​20–40 minutes, and the operating time for the remaining tanks is 5–10 minutes. After cleaning, the product surface must show the natural metal color, and no black spots, blemishes, or other contaminants are allowed. During handling, clean white gloves must be worn, and direct hand contact with the product is prohibited.

[0028] 2. Surface roughness control: Wet sandblasting is used with a sandblasting pressure of 0.5-0.8MPa and a sandblasting time of 20-40min to remove contaminants with strong adhesion and increase the surface roughness of the product.

[0029] 3. Control of Dryness: The main control method of this invention is drying before loading into the furnace, which involves maintaining the temperature at 80~110℃ in a clean environment for 1~3 hours. The purpose of this is to drive out water molecules adhering to the product surface, preventing them from decomposing and reacting with the product under high-temperature heating.

[0030] 4. Controlling the cleanliness of the furnace: This involves performing periodic maintenance and preheating the furnace before heat treatment to achieve a clean furnace.

[0031] The key points of pretreatment control are shown in Table 1.

[0032] Table 1. Key Control Points and Operational Requirements for Pretreatment Serial Number Control Content Key Control Points Operating requirements Inspection methods 1 Cleaning quality The metal should be exposed to its natural color; there should be no black spots, blemishes, or other sources of contamination; and there should be no large areas of water stains or other residual cleaning agents. Wear clean white gloves and do not directly touch the sample. Visual inspection 2 Dryness The surface feels dry. Dry at 80~110℃ for 1~3 hours touch 3 Surface roughness Non-smooth surface Sandblasting Visual inspection 4 Furnace cleanliness Dedicated furnace for regular maintenance and drying Titanium alloy solution treatment furnaces are not permitted to process products other than titanium alloys; the furnace chamber must be wiped down weekly or monthly. Process Discipline Inspection

[0033] The control technology for titanium alloy heat treatment mainly includes four key points: 1. Control of furnace charging method: When using the tooling designed in this invention and its adapted loading method for loading into the furnace, the effective loading amount (i.e. the weight of the processed product, excluding the weight of the tooling) shall not exceed 20 kg.

[0034] 2. Control the heating process. The heating rate must not exceed 25℃ / min to ensure that all parts undergoing heat treatment reach the set temperature.

[0035] 3. Medium control: Whether argon is used as a cooling atmosphere or a protective atmosphere, its dew point should be controlled below -55℃.

[0036] 4. Continuous titanium shavings protection: To control the reaction between the contaminant and the titanium alloy, this invention specifies that the surface of the titanium alloy parts be wrapped with continuous titanium shavings. The continuous titanium shavings are prepared by turning and should be spiral-shaped. Titanium shavings with a length of less than 2cm are not allowed. The volume ratio of titanium shavings to parts is 3-5 times. After laying the titanium shavings, titanium wire is used to further fix the titanium shavings to the product.

[0037] The key points of process control technology are shown in Table 2.

[0038] Table 2. Operational Information Table for Heat Treatment Process Control Technology Serial Number Control Content Key Control Points Operating requirements Inspection methods 1 Furnace loading method Furnace loading amount, charging interval Furnace loading ≤20kg Weighing 2 heating process Preheating temperature, preheating time, heating rate The temperature gradient meets the requirements, and the holding time can guarantee the temperature. Visual instruments 3 Pollution source control Argon dew point, titanium scrap protection True argon dew point ≤ -55℃ Visual instruments

[0039] The adaptable tooling designed in this invention includes: (1) One-way cap made of ceramic matrix composite material This component is made of ceramic matrix composite material and has a vent at the top, which is connected by a one-way valve. Its function is as follows: Firstly, ceramic matrix composites have properties such as high temperature resistance, oxidation resistance, and low coefficient of thermal expansion. They can maintain their designed shape at high temperatures without changing and do not react with the atmosphere or the metals they come into contact with. Secondly, the one-way valve is mainly used to remove residual air or moisture from the chamber and prevent external gas from entering, thus achieving one-way gas control. Its principle is that when the entire furnace is evacuated, the gas pressure inside the chamber is greater than the furnace pressure. At this time, the one-way valve opens, venting the residual gas inside the chamber and achieving pressure balance. When the gas pressure inside the chamber is less than the furnace pressure, the one-way valve closes, ensuring that the vacuum level inside the chamber remains high, thereby preventing residual air from reacting with the titanium alloy surface in an oxidation reaction.

[0040] Aerogel gasket The main function of aerogel gaskets is heat insulation and sealing. The main material is zirconia aerogel, which has excellent high-temperature stability and high-temperature chemical stability. It can play a role in heat insulation while preventing large particulate pollutants in the furnace from entering the box and preventing titanium alloy from contacting the pollution source.

[0041] Box The main function of the enclosure is the same as that of the heat treatment fixtures, primarily used for placing or mounting titanium alloy parts to be processed. A variety of materials can be selected, such as stainless steel.

[0042] Rotatable bearing The device is fixed inside the box and its main function is to connect the box and the tooling mesh. In use, the tooling mesh is raised and lowered by rotating bearings to realize the loading of parts of different layers.

[0043] Workwear Network The main function of this device is to lay or place titanium alloy parts. Generally, there are 2-3 layers of tooling mesh in a set of devices. When loading the furnace, all tooling meshes are first lifted by rotating bearings, and the lower layer of tooling meshes are placed first. Then, they are laid layer by layer to complete the loading of the furnace.

[0044] pad block This device is used in pairs with the tooling mesh and mainly serves as a barrier. Its placement is aligned with the rotating bearing. Each set of pads consists of 2-3 pieces on the same horizontal plane to ensure that the parts loaded into the furnace are evenly distributed on the tooling mesh.

[0045] Pre-vacuum valve The main function of this device is to add a pre-vacuum environment to the box containing the parts, so that there are as few gases and contaminants as possible inside the box. At the same time, during the heat treatment process, as the vacuum degree of the furnace gradually decreases, the pre-vacuum inside the box gradually reaches equilibrium with the furnace. During this process, the gas pressure in the evacuated box is always lower than that in the furnace, and the one-way valve is always closed, which can effectively prevent external gases and contaminants from entering the box.

[0046] Example 1: Using the technical method specified in this invention, the process control parameters are as follows: Pre-processing stage: First and second tanks: Alkaline metal cleaning agent (concentration 3%, temperature 70℃, treatment time 30 minutes).

[0047] Third tank: Spray with room temperature clean water (5 minutes).

[0048] Fourth tank: Acidic cleaning agent (concentration 2%, temperature 70℃, treatment time 8 minutes).

[0049] Fifth bath: hot water rinse (80℃, 8 minutes).

[0050] Sixth tank: Spin dry (temperature 70℃, time 30 minutes).

[0051] Sandblasting: Wet sandblasting treatment, pressure 0.6 MPa, time 30 minutes.

[0052] Drying: Keep warm at 100℃ for 2 hours.

[0053] 2. Loading and Protection: Using the tooling box of this invention, the loading capacity is 15 kg. Lay out spiral-shaped titanium shavings (length ≥ 2 cm, volume 4 times the volume of the part) and fix them with titanium wire. Cover with a ceramic matrix composite one-way cover and perform pre-vacuuming.

[0054] 3. Solution heat treatment: Heating rate: 20℃ / min. Preheating stage: 650℃ for 30 minutes → 850℃ for 30 minutes. High-temperature solution treatment: 1030℃ for 60 minutes. Vacuum degree: 1.33×10⁻⁶ -2 Pa. Cooling: Cool the argon gas to room temperature; the argon dew point is ≤-55℃.

[0055] 4. Aging heat treatment: Directly transfer to the aging furnace, heating rate 20℃ / min. Aging conditions: 750℃ for 4 hours. Vacuum degree: 1.33×10⁻⁶ -2 Pa. Cooling: Argon gas cooling.

[0056] The depth of the surface contamination layer is controlled to ≤0.05 mm, which meets the requirements of standards such as HB8025 (≤0.08 mm). No additional turning or pickling processes are required, saving materials and processing time.

[0057] See Figures 8-9 The titanium alloy parts heat-treated using this invention retained their metallic color and did not exhibit the oxidation color that often occurs during heat treatment, indicating that surface quality control is more advanced than existing heat treatment techniques. Furthermore, metallographic observation of the heat-treated parts revealed a uniform microstructure, no dense α-phase formation on the surface, and almost no contamination layer, achieving the expected goals.

[0058] Comparative Example 1: The difference from Example 1 is as follows: The heat treatment process parameters specified in the standard are adopted, using a common vacuum furnace, without a dedicated enclosure, titanium shavings protection, or one-way valve control. See below: Solution heat treatment: 1030℃×60min, cooled in argon, with a process vacuum of 1.33×10-2Pa; Aging heat treatment: 750℃×4h, cooled in argon gas, with a process vacuum of 1.33×10-2Pa.

[0059] See Figures 10-11The titanium alloy parts that have undergone heat treatment exhibit a bluish-black surface, consistent with current industry practices, and show obvious oxide formation on the surface. Further metallographic observation of the microstructure revealed a uniform internal structure, similar to that of the example sample. However, a dense α-layer exceeding 0.1 mm in thickness appeared at the surface edges, indicating that standard heat treatment processes would result in a thicker contamination layer on the surface, failing to meet the expected performance requirements.

[0060] Comparative Example 2 The difference from Example 1 is as follows: Using standard tooling, without a dedicated enclosure, but with titanium shavings protection, vacuum sealing, the effect is as follows: Figure 12 As shown. Metallographic observation of the microstructure of the heat-treated titanium alloy parts revealed that the internal structure of the parts was uniform and similar to that of the example. However, a dense α layer with a thickness exceeding 0.08 mm appeared at the edge of the part surface. This indicates that adding titanium shavings protection helps to alleviate the formation of the surface contamination layer, but the effect is not very significant. A relatively thick contamination layer still forms on the surface of the parts, which cannot meet the expected usage requirements.

[0061] Comparative Example 3 The tooling of this invention was used, but pre-vacuuming was not performed. Other steps were the same as in Example 1, and the effect was as follows: Figure 13 As shown. The titanium alloy parts heat-treated using the tooling designed in this invention were subjected to metallographic observation. The results showed that the microstructure was uniform, no dense α phase was formed on the surface of the parts, and the depth of the surface contamination layer was less than 0.05 mm, achieving the expected goal.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A tooling for controlling the depth of a surface contamination layer of a titanium alloy, characterized in that: include: The enclosure has an opening at the top for accommodating titanium alloy parts to be processed. The top cover assembly is connected to the opening of the box body. The top cover assembly includes a ceramic matrix composite one-way cover and a one-way exhaust valve. The ceramic matrix composite one-way cover is provided with several vent holes, and the one-way exhaust valve is installed at the vent holes. A sealing element is provided at the junction of the housing and the sealing cover assembly, and the sealing element is an annular aerogel gasket; The internal support mechanism includes several internal support components, which are housed within the enclosure. A pre-vacuum valve is located on the housing.

2. The tooling for controlling the depth of surface contamination layer of a titanium alloy according to claim 1, characterized in that: The internal load-bearing components include tooling mesh and pad blocks; One end of the tooling mesh is set inside the box via a rotatable bearing, and the other end is set on the top of the pad block; The pad is placed inside the housing and corresponds to the position of the rotatable bearing.

3. The tooling for controlling the depth of surface contamination layer of a titanium alloy according to claim 1, characterized in that: The tooling mesh is woven from high-temperature resistant metal wire; And / or, the pad is made of stainless steel or a nickel-based high-temperature alloy; And / or, the number of internal carrier components is at least 2.

4. The tooling for controlling the depth of surface contamination layer of a titanium alloy according to claim 1, characterized in that: The one-way exhaust valve is a reed or diaphragm vacuum differential pressure valve. It opens to exhaust when the internal air pressure is higher than the external pressure, and closes when the internal air pressure is equal to or lower than the external pressure.

5. The tooling for controlling the depth of surface contamination layer of a titanium alloy according to claim 1, characterized in that: The cyclic aerogel gasket is a zirconia cyclic aerogel gasket.

6. A method for controlling the depth of a surface contamination layer of a titanium alloy, a tool for controlling the depth of a surface contamination layer of a titanium alloy according to any one of claims 1 to 5, characterized in that: Includes the following steps: S1: Pretreatment of titanium alloy parts to be processed; S2: Lay titanium shavings layer by layer on the internal load-bearing components, place the titanium alloy parts to be processed on the titanium shavings, and then lay them on with titanium shavings. S3: Perform solution treatment and aging treatment.

7. The method of claim 6, wherein: Step S1 involves the following pretreatment steps for the titanium alloy parts to be processed: A1: A multi-tank cleaning system is used to clean the titanium alloy workpiece to be treated. The cleaning system includes a first tank, a second tank, a third tank, a fourth tank, a fifth tank, and a sixth tank arranged in sequence; the first and second tanks are alkaline metal cleaning agent tanks; the third tank is a clean water spray tank; the fourth tank is an acidic cleaning agent tank; the fifth tank is a hot water rinsing tank; and the sixth tank is a spin-drying tank. A2: Perform wet sandblasting and drying on the cleaned workpiece.

8. The method for controlling the depth of contamination layer on a titanium alloy surface according to claim 7, characterized in that: The concentration of the alkaline metal cleaning agent in the first and second tanks is 2% to 5%, the heating temperature is 60 to 80°C, and the processing time of the workpiece in each tank is 20 to 40 minutes. And / or, the third tank is cleaned by a water spray tank at room temperature or low temperature for 5 to 10 minutes. And / or, the acid cleaning agent concentration in the acid cleaning agent tank of the fourth tank is 1% to 3%, the heating temperature is 60 to 80°C, and the treatment time is 5 to 10 minutes; And / or, the hot water rinsing time in the fifth tank is 5 to 10 minutes; And / or, the heating temperature of the spin-drying tank in the sixth tank is 60-80℃, and the spin-drying time is 20-40 minutes; And / or, the surface of the cleaned workpiece should reveal the original metal color, with no visible black spots, black patches or water stains remaining, and the operator must wear clean gloves during handling; And / or, in step A2, the sandblasting pressure for wet sandblasting the cleaned workpiece is 0.5 to 0.8 MPa, and the sandblasting time is 20 to 40 minutes; And / or, the drying temperature in step A2 is 80~110℃, and the holding time is 1~3h.

9. The method for controlling the depth of contamination layer on a titanium alloy surface according to claim 7, characterized in that: In step S2, titanium chips are produced by turning, are spiral in shape, and have a length of not less than 2 cm. The total volume of titanium chips is 3 to 5 times the total volume of the part. After laying the titanium chips, titanium wire is used to fix the titanium chips to the part. The furnace loading capacity of the box shall not exceed 20kg, and the interval between reloading shall be at least 5 minutes. The weight of the titanium alloy parts to be processed each time shall not exceed 1kg.

10. The method for controlling the depth of contamination layer on a titanium alloy surface according to claim 7, characterized in that: The solution heat treatment in step S3 is holding at 600-700℃ and 800-900℃ for 25-35 minutes, then holding at 1000-1050℃ for 55-65 minutes, and the vacuum degree during the process is 1.3-1.4*10 -2 Pa; after the holding, cooling to room temperature in argon; The aging heat treatment in step S3 does not need to reload the parts, and the box is directly transported to the aging furnace, the temperature is 700-800℃, the time is 3-5h, and the vacuum degree in the process is 1.33x10 -2 Pa; The heating rate for solution treatment and aging in step S3 shall not exceed 25°C / min; The protective or cooling atmosphere used in the solution heat treatment and aging heat treatment in step S3 is argon, and its dew point is not higher than -55℃.

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